The importance of duodenogastro-oesophageal reflux (DGOR) in gastro-oesophageal reflux disease (GORD) is controversial. Most evidence points to a possible synergistic effect between refluxed acid and bile, which may be more frequent in patients with Barrett's oesophagus, particularly those with complications. Techniques for long-term measurement of DGOR include continuous aspiration, which is cumbersome and laborious, ambulatory spectrophotometric bilirubin measurement as a proxy for bile acids and sodium ion measurement using a sodium electrode. The two latter are the most promising techniques which are improving understanding of DGOR in clinical situations. Both have advantages and drawbacks. The Bilitec system for measuring bilirubin has been most studied and has been well validated. The sodium electrode has so far only been used for short-term monitoring but may be capable of development into a practical tool for longer-term monitoring of DGOR.